1. Field of the Invention
The present invention relates generally to the production of methanol from the reaction of carbon monoxide and carbon dioxide with hydrogen in the presence of a copper/zinc/alumina catalyst and in particular in a catalytic distillation process. More particularly, the invention relates to the use of an inert component in a catalytic distillation column wherein the inert component is boiling and condensing around the normally gaseous reactants.
2. Related Art
Methanol is one of the basic chemicals and as such is produced at an annual rate of over 10 million tons. Conventionally methanol has been produced in two-phase systems: The reactants (CO, CO.sub.2, and H.sub.2) and products (mainly CH.sub.3 OH and H.sub.2 O) forming the gas phase and the catalyst being the solid phase. In a methanol plant, the reaction of carbon monoxide, carbon dioxide and hydrogen is exothermic. Thus in a conventional fixed bed reactor design, heat control and removal is of prime importance. If too much CO.sub.2 or CO is present, the reactor can overheat and damage the catalyst. As a result, for a given catalyst, a liquid phase reactor was preferable under the prior technology, because the basic characteristics of a liquid phase reactor allow it to be cooled internally.
More recently a three-phase methanol synthesis process (now known under the trademark LPMEOH) has been developed. In that process an inert liquid phase is introduced into the reactor, mainly to absorb heat released during the reaction. Heat transfer between the solid catalyst and the liquid phase is highly efficient, thereby allowing higher conversions to be obtained without impairment of catalyst activity. The liquid phase allows for the removal of heat by use of an internal heat exchanger in the LPMEOH process. The solid particulate catalyst is introduced in a slurry of the inert liquid.
The following three equations may be used to empirically represent the reactions going on during the present process: EQU CO+2H.sub.2 .revreaction.CH.sub.3 OH (1) EQU CO.sub.2 +H.sub.2 .revreaction.CO+H.sub.2 O (2) EQU CO.sub.2 +3H.sub.2 .revreaction.CH.sub.3 OH+H.sub.2 O (3)
Catalytic distillation, in which reaction products are produced and concurrently separated from reactants by distillation, has been used successfully to control temperatures in exothermic reactions. However, the use of catalytic distillation has been traditionally limited by the fact that one of the reactants must be a boiling liquid at the conditions inside the reactor. In the earlier catalytic distillation processes both reactants were fed to the reactor as liquids. More recently, U.S. Pat. No. 5,087,780 has shown that the catalytic distillation method is useful in a process wherein hydrogen is a reaction component. Inert materials have been fed to a catalytic distillation for various purposes, such as to provide a heat sink, but always one of the reactants has been a boiling liquid